1. Field of the Invention
The present invention relates generally to a protection film structure for functional devices, and particularly to the protection film structure for functional devices which are protected from humidity, for instance: a sensor array, memory devices, a magnetic recording medium, etc.
2. Description of the Related Art
Protection film for protecting a functional device, functional film structure or functional material has been used to improve reliability of the functional device or the like. For such protection film, hitherto inorganic material such as silicon oxide, glass, etc. and organic materials such as polyimido, Varilene (trade mark), etc. have been used. These protection films have been used in limited uses for protecting small areas, but recent technology requires protection of large areas of functional devices such as sensor arrays, recorded discs, recorded tapes, etc. to improve resistance against humidity and abrasion.
Especially, recent development of electronic devices strongly requires forming of a protection film which has a different thermal expansion coefficient from that of the substrate, or forming of a uniform protection film under a low temperature such as room temperature.
However, the conventional art has not been able to provide a satisfactory protection film configuration to satisfy the above-mentioned requirements both in characteristics and from an economic view point.
The inventors experimentally found a novel construction of a protection film structure for functional devices which can satisfactorily fulfil the above-mentioned requirements.